Cleaning composition



Patented Mar. 19, 1946 CLEANING COMPOSITION Alfred Douty, Elkins Park,and Ferdinand Heller,

Philadelphia, Pa., assignors to American Chemical Paint Company, Ambler,Pa., a corporation of Delaware No Drawing. Application March 18, 1943,-Serial N0. 479,594

2 Claims. (Cl. 252-143) even strong mechanical action is not generallyThis invention relates to the art of cleaning metals, and isparticularly concerned with the provision of an improved cleaningcomposition for this purpose. It is especially useful in the cleaning offerrous metal surfaces, although not limited thereto.

The objects of the invention will be better understood and more fullyappreciated if certain of the practices now familiar to the art arebriefly mentioned. For instance, it has long been the practice to cleanand prepare surfaces of iron, steel, aluminum, etc. for the reception ofpaint or the like by the use of solutions of phosphoric acid containingone or more solvents together with compatible wetting agents,emulsifying agents, inhibitors of acid attack on the metal, etc. Amongthe solvents so employed may be mentioned alcohols from methanol to amylalcohols, inclusive, ketones, such as acetones, methyl ethyl ketone, anddiacetone alcohol; alcohol-ethers, such as the ethers of ethylene glycolor diethylene glycol; and many more from other classes. These are greasesolvents and are both water soluble or miscible and oil soluble, andtheir presence in cleaning solutions tends to dissolve the oil or greaseon the work to be cleaned, thereby diluting and thinning it and loweringits surface tension. This produces a tendency for the oily or greasycontaminant to draw up into droplets so that it'can be more readilyemulsified by mechanical action.

Among the wetting agents which have been used heretofore are sulfatedoils such as "sulfonated castor oil, cottonseed oil, etc.; sulfonatedhydrocarbons, e. g., alkylated naphthalene sulfonic acids; sulfatedalcohols of six or more carbon atoms, of straight or branched chain;sulfonated esters as of succinic acid, etc. These wetting agents alsoexhibit more or less emulsifying powers although other emulsifyingagents have generally been employed in cleaning compositions of thisgeneral nature such, for example, as water soluble gums like gum arabicand gum tragacanth; gelatine or glue; molasses; soap bark extracts orpurified saponins; and numerous others.

In connection with cleaners of the general nature just described it hasbeen our experience that cleaning compositions which include solutionsof phosphoric acid containing only the wetting and/or emulsifying agentsare not capable of completely removing the greasy or oily mattertogether with the dirt from the surface of the metal, and that it isonly where adequate quantities of the water miscible solvents arepresent that the compositions are capable of reasonably thoroughlyremoving the grease and the dirt. Apparently this is due to the factthat the wetting agents per se seem to cause the solution to spread overthe top 1' tha able to cause the solution to penetrate the grease and tospread over the metal therebeneath without the addition of the watermiscible grease solvents mentioned above.

However, the water miscible grease solvents ordinarily in use have nowbecome of strategic importance in the war effort, and therefore are notreadily available for many of the purposes for which they were formerlyemployed.

With the foregoing in mind the principal objects of our invention are toprovide a cleaner which will remove oxide, dirt and greasy or oilysubstances while at the same time putting the surface of the metal inthe best possible condition for the reception of an organic protectiveor finish coating, such as paint, varnish, lacquer, japan and the like;to provide a metal cleaner of greatly improved grease, oil and dirtremoving efficiency which does not require the relatively scarce andexpensive water miscible solvents above discussed; to produce arelatively much more concentrated and more highly dilutable cleaningcomposition than has heretofore been possible with compositions known tothe art wherein large volumes of water miscible solvents are included;to provide a cleaner which is exceptionally useful in removing heavyviscous greases from metal surfaces to which end we employ waterimmiscible solvents emulsified with phosphoric acid solutions; toproduce a cleaner which can be applied by means of a spray without thetroublesome foaming which, under spraying conditions, would otherwise beassociated with the presence of the emulsifying agent; to provide acleaning composition which, because of its unusually concentratedcharacter, can be more readily and cheaply packaged and transported; andin general to im.. prove the efficiency, availability and all-roundusefulness of a cleaner of this type.

We have discovered that remarkable cleaning action may be obtained onordinary oily or greasy surfaces by means of an aqueous phosphoric acidsolution which includes small quantities of water soluble, non-ionicemulsifying agents such as the tertiary alkylarylpolyglycols representedby the general formula:

in which formula m is at least 8, CmH2m+1 is a tertiary alkyl group andn equals 10 or more, depending on the nature and weight of thesubstituent groups. Compounds having a polyglycol chain of such lengthare appreciably soluble in water and the water solubility remainsappreciable to very high values of n lea An admixture of dilutephosphoric acid containing a small amount of emulsifying agent of theabove type wets oily steel readily: when applied freely with a brush orrag, for example, the oil or light grease on the surface, is rapidlyemulsified and removed from the surface together with any adhering dirt.Simultaneously, the acid solution thoroughly and evenly wets the surfaceof the metal and dissolves light oxideor rust therefrom. If the surfacebe now washed with water, it will be found to be completely grease freeand will exhibit no "water break. The cleanliness of the surfaceobtained is remarkable and, in our experience, is superior to thatobtainable with any previous cleaner of the phosphoric acid type. evenwhen these previous types contain substantial amounts of oil solvent.

An example of a concentrated composition Phosphoric acid, 75% gallon0.9500 Emulsifying agent pound 0.16 Water, to make gallon 1.000

The amount of water used in diluting the above formula depends on theamount of rust or oxide to be removed from the surface, as well as onthe kind and amount of grease present.

In general, from one to eight volumes of water per volume of Formula No.1 sho ld be added in diluting the material for use, although we havefound that for ordinary sheet steel art cles, such as automobile ortruck bodies. refrigerators, etc., about four volumes of wat r to one ofFormula No. 1 is usually the most satisfactory.

The diluted material maybe applied to the surface to be cleaned bybrushing. sprayin flowing or by dipping the work into the sol tion. Inmost cases. removal of oil will be facilitated by gently rubb ng t esurface. as with a brush or r r y f r f l y appl ng the solution to themetal, as by spraying,

The surface is then washed with water. and dried by any convenientmeans. whe eupon it will be found to be very clean and ready forpainting. etc.

It may be noted that verv clean steel surfaces such as are produced bvthe action of our improved cleaners. rapidly acouire a film of oxide ifallowed to stand wet with water. Ra id drying is. therefore. advisableafter the cleaning operation. However. oxide formed on the surface aftercleaning with our novel cleaner is inert," i. c. it contains norust-stimulative material and is thus innocuous under paint or the like.

For exceptionally greasy work or when the cleaning solution is to beapplied to the work byforceful spraying in a recirculating system weprefer to use a material in which is emulsified a water immisciblesolvent such as a petroleum naphtha according to the following example:

The above concentrated material is violently stirred, passed through-ahomogenizer, or otherwise brought to a uniform emulsion by ordinaryknown means.

For use in a recirculating spray washing machine, it is diluted withfrom 3 to 19 volumes of water and forcefully sprayed upon the work to becleaned, for about 15 to 60 seconds, more or less. The run 01! solutionis collected and reused. After rinsing and drying the work will be foundto be thoroughly cleaned.

The emulsified solvent in this material has the effect of diluting, andthus thinning out and makingv easier to remove any heavy grease on thesurface of the work." Moreover, the strong foaming tendency of thesolution is repressed by the solvent, thus preventing the solution fromfoaming out over the top of the spray collecting tank.

The diluted solutions of both Formulas No. 1 and No. 2 may be usedeither at room temperature or at elevated temperature. More rapidcleaning action is obtained, of course, at elevated temperatures whichmay be as high as the boiling point of the diluted phosphoric acid or ofthe solvent, whichever is the lower.

It must be noted, however, that it may involve some fire hazard tooperate the cleaning solution above the flash point of the solvent used.This can be avoided, of course, by the use of noninfiammable solvents,as noted below.

The above examples are to be taken, qualitatively and quantitatively, asillustrative but not as limiting the scope of the invention.

For instance, the amounts of phosphoric acid and emulsifying agent ofthe type described may be varied within wide limits without departingfrom the spirit of the invention. If the work to be cleaned is veryrusty, or if considerable etching of thesurface is desirable, thephosphoric acid concentration is maintained high (up to 70% by volume of75% phosphoric acid or even more, if desired, in the cleaner as dilutedfor use). If the work has little greasy or oily contamination theemulsifier concentration need not exceed 0.05% or even less.

On the other hand, for work which is not rusty or need not be etched,phosphoric acid concentrations as low as 0.5% by volume of 75% HaPOi, oreven less, may be sufficient. If the work is very greasy the cleaningsolution may contain as high as 2% or even more of emulsifying agent,although more than 0.5% would rarely be required.

In formulations including water-immiscible solvents like the Stoddardsolvent above mentioned, a great variety of such is permissible. Theonly limitation on the water-immiscible solvents which may be selectedis that they must be good grease solvents, and that they must not be toovolatile at the temperature at which the cleaner is to be used.

As examples of water-immiscible solvents which have been found usefulare: hydrocarbon solvents such as toluene, petroleum spirits of variousboiling ranges, hydrogenated petroleum solvents, high-flash coal tarnaphtha, decahydronaphthalene, pine oil, chlorinated hydrocarbons suchas carbon tetrachloride, trichlorethyiene, tetrachloroethane, etc.; andmany others.

The chlorinated solvents may be used where the fire hazard attendantupon the use of inflammable solvent is serious.

The amount of water-immiscible solvent, on the one hand, in relation tothe phosphoric acid and the emulsifying agent, on the other hand, mayvary over a, considerable range subject, of course, to the limitationsimposed by the total quantity of the latter two which may be requiredfor the particular work in hand.

Although, in the interest of economy of storage space and reduction intransportation costs, it is both preferable and desirable to prepare ournovel cleaner in the form of a concentrated admixture capable ofrelatively high dilution before use, it will be obvious that there is noreason why acid, emulsifying agent and/or solvent may not be separatelyadded to the diluted material to alter their relative proportions, ifnecessary.

The emulsifying agents which we have found useful in the presentinvention dissolve in water to produce foamy solutions of low surfacetension and great emulsifying power for oily matter in water. Thecompounds are not ionized in water and when used in cleaners of the typedescribed are readily rinsed from metal surfaces together with theemulsified grease, suspended dirt, excess acid, reaction products of theacid and the metal, etc., leaving behind no deleterious orruststimulative ions. Such emulsifying agents are truly non-ionic, andwe prefer to describe the useful species of agents of the class underdiscussion as water-soluble, non-ionic emulsifying agents of the classof polyethyleneglycols substituted in one terminal hydroxyl group withan alkyl-aryl radical.

In contradistinction to the desired materials, similar compounds of lowchain length such for example as alpha, alpha, gamma,gamma-tetramethylbutyl-phenoXy-ethanol are insoluble oils. They can besolubilized by introducing polar groups such as I-ISO: or H804 intotheir molecules, but such polar groups make the resulting compoundsionic in nature, 1. e. they yield charged ions when dissolved in water.Such ionic compounds are not suitable for this invention. Although theywill wet and emulsify well, they may leave behind, on work cleaned witha solution containing them, traces of rust-stimulative anions. We thuswish to limit ourselves to compounds of the class described which arenonionic and are appreciably water soluble, per se.

A wide variety of suitable materials is available to the chemist. Theymay be prepared, in general, by treating the halides or halohydrins ofthe polyethylene-glycols with fatty acids, alcohols or phenols in thepresence of alkali metal hydroxide or carbonates.

To our cleaning preparations as described hereinabove may be added, ifdesired, any compatible proportion of water miscible solvent, inhibitor,thickening agent, oil, etc., without departing from the spirit of theinvention. Such additions are not ordinarily necessary, but may haveusefulness for special applications.

We claim:

1. A solution for cleaning metal preparatory to painting includingwater, phosphoric acid, and tertiary alkylarylpolyglycol represented bythe formula:

in which in is at least 8, CmH2m+1 is a tertiary alkyl group and nequals at least 10.

2. The composition of claim l which also includes emulsifiedsubstantially water-insoluble grease solvent.

ALFRED DOUTY. FERDINAND HELLER.

